Demonstrating the utility of the ex vivo murine mycobacterial growth inhibition assay (MGIA) for high-throughput screening of tuberculosis vaccine candidates against multiple Mycobacterium tuberculosis complex strains

Human tuberculosis (TB) is caused by various members of the Mycobacterium tuberculosis (Mtb) complex. Differences in host response to infection have been reported, illustrative of a need to evaluate efficacy of novel vaccine candidates against multiple strains in preclinical studies. We previously showed that the murine lung and spleen direct mycobacterial growth inhibition assay (MGIA) can be used to assess control of ex vivo mycobacterial growth by host cells. The number of mice required for the assay is significantly lower than in vivo studies, facilitating testing of multiple strains and/or the incorporation of other cellular analyses. Here, we provide proof-of-concept that the murine MGIA can be applied to evaluate vaccine-induced protection against multiple Mtb clinical isolates. Using an ancient and modern strain of the Mtb complex, we demonstrate that ex vivo bacillus Calmette-Guérin (BCG)-mediated mycobacterial growth inhibition recapitulates protection observed in the lung and spleen following in vivo infection of mice. Further, we provide the first report of cellular and transcriptional correlates of BCG-induced growth inhibition in the lung MGIA. The ex vivo MGIA represents a promising platform to gain early insight into vaccine performance against a collection of Mtb strains and improve preclinical evaluation of TB vaccine candidates.

Single Nucleotide Polymorphisms in the Bovine TLR2 Extracellular Domain Contribute to Breed and Species-Specific Innate Immune Functionality

Recent evidence suggests that several cattle breeds may be more resistant to infection with the zoonotic pathogen Mycobacterium bovis. Our data presented here suggests that the response to mycobacterial antigens varies in macrophages generated from Brown Swiss (BS) and Holstein Friesian (HF) cattle, two breeds belonging to the Bos taurus family. Whole genome sequencing of the Brown Swiss genome identified several potential candidate genes, in particular Toll-like Receptor-2 (TLR2), a pattern recognition receptor (PRR) that has previously been described to be involved in mycobacterial recognition. Further investigation revealed single nucleotide polymorphisms (SNP) in TLR2 that were identified between DNA isolated from cells of BS and HF cows. Interestingly, one specific SNP, H326Q, showed a different genotype frequency in two cattle subspecies, Bos (B.) taurus and Bos indicus. Cloning of the TLR2 gene and subsequent gene-reporter and chemokine assays revealed that this SNP, present in BS and Bos indicus breeds, resulted in a significantly higher response to mycobacterial antigens as well as tri-acylated lipopeptide ligands in general. Comparing wild-type and H326Q containing TLR2 responses, wild-type bovine TLR2 response showed clear, diminished mycobacterial antigen responses compared to human TLR2, however bovine TLR2 responses containing H326Q were found to be partially recovered compared to human TLR2. The creation of human:bovine TLR2 chimeras increased the response to mycobacterial antigens compared to the full-length bovine TLR2, but significantly reduced the response compared to the full-length human TLR2. Thus, our data, not only present evidence that TLR2 is a major PRR in the mammalian species-specific response to mycobacterial antigens, but furthermore, that there are clear differences between the response seen in different cattle breeds, which may contribute to their enhanced or reduced susceptibility to mycobacterial infection.

Strain Specific Variations in Acinetobacter baumannii Complement Sensitivity

The complement system is required for innate immunity against Acinetobacter baumannii, an important cause of antibiotic resistant systemic infections. A. baumannii strains differ in their susceptibility to the membrane attack complex (MAC) formed from terminal complement pathway proteins, but the reasons for this variation remain poorly understood. We have characterized in detail the complement sensitivity phenotypes of nine A. baumannii clinical strains and some of the factors that might influence differences between strains. Using A. baumannii laboratory strains and flow cytometry assays, we first reconfirmed that both opsonization with the complement proteins C3b/iC3b and MAC formation were inhibited by the capsule. There were marked differences in C3b/iC3b and MAC binding between the nine clinical A. baumannii strains, but this variation was partially independent of capsule composition or size. Opsonization with C3b/iC3b improved neutrophil phagocytosis of most strains. Importantly, although C3b/iC3b binding and MAC formation on the bacterial surface correlated closely, MAC formation did not correlate with variations between A. baumannii strains in their levels of serum resistance. Genomic analysis identified only limited differences between strains in the distribution of genes required for serum resistance, but RNAseq data identified three complement-resistance genes that were differentially regulated between a MAC resistant and two MAC intermediate resistant strains when cultured in serum. These data demonstrate that clinical A. baumannii strains vary in their sensitivity to different aspects of the complement system, and that the serum resistance phenotype was influenced by factors in addition to the amount of MAC forming on the bacterial surface.

Probing Differences in Gene Essentiality Between the Human and Animal Adapted Lineages of the Mycobacterium tuberculosis Complex Using TnSeq

Members of the Mycobacterium tuberculosis complex (MTBC) show distinct host adaptations, preferences and phenotypes despite being >99% identical at the nucleic acid level. Previous studies have explored gene expression changes between the members, however few studies have probed differences in gene essentiality. To better understand the functional impacts of the nucleic acid differences between Mycobacterium bovis and Mycobacterium tuberculosis, we used the Mycomar T7 phagemid delivery system to generate whole genome transposon libraries in laboratory strains of both species and compared the essentiality status of genes during growth under identical in vitro conditions. Libraries contained insertions in 54% of possible TA sites in M. bovis and 40% of those present in M. tuberculosis, achieving similar saturation levels to those previously reported for the MTBC. The distributions of essentiality across the functional categories were similar in both species. 527 genes were found to be essential in M. bovis whereas 477 genes were essential in M. tuberculosis and 370 essential genes were common in both species. CRISPRi was successfully utilised in both species to determine the impacts of silencing genes including wag31, a gene involved in peptidoglycan synthesis and Rv2182c/Mb2204c, a gene involved in glycerophospholipid metabolism. We observed species specific differences in the response to gene silencing, with the inhibition of expression of Mb2204c in M. bovis showing significantly less growth impact than silencing its orthologue (Rv2182c) in M. tuberculosis. Given that glycerophospholipid metabolism is a validated pathway for antimicrobials, our observations suggest that target vulnerability in the animal adapted lineages cannot be assumed to be the same as the human counterpart. This is of relevance for zoonotic tuberculosis as it implies that the development of antimicrobials targeting the human adapted lineage might not necessarily be effective against the animal adapted lineage. The generation of a transposon library and the first reported utilisation of CRISPRi in M. bovis will enable the use of these tools to further probe the genetic basis of survival under disease relevant conditions.

Sequential Vaccination With Heterologous Acinetobacter baumannii Strains Induces Broadly Reactive Antibody Responses

Antibody therapy may be an alternative treatment option for infections caused by the multi-drug resistant (MDR) bacterium Acinetobacter baumannii. As A. baumannii has multiple capsular serotypes, a universal antibody therapy would need to target conserved protein antigens rather than the capsular polysaccharides. We have immunized mice with single or multiple A. baumannii strains to induce antibody responses to protein antigens, and then assessed whether these responses provide cross-protection against a collection of genetically diverse clinical A. baumannii isolates. Immunized mice developed antibody responses to multiple protein antigens. Flow cytometry IgG binding assays and immunoblots demonstrated improved recognition of both homologous and heterologous clinical strains in sera from mice immunized with multiple strains compared to a single strain. The capsule partially inhibited bacterial recognition by IgG and the promotion of phagocytosis by human neutrophils. However, after immunization with multiple strains, serum antibodies to protein antigens promoted neutrophil phagocytosis of heterologous A. baumannii strains. In an infection model, mice immunized with multiple strains had lower bacterial counts in the spleen and liver following challenge with a heterologous strain. These data demonstrate that antibodies targeting protein antigens can improve immune recognition and protection against diverse A. baumannii strains, providing support for their use as an antibody therapy.

Re-sensitization of Mycobacterium smegmatis to Rifampicin Using CRISPR Interference Demonstrates Its Utility for the Study of Non-essential Drug Resistance Traits

A greater understanding of the genes involved in antibiotic resistance in Mycobacterium tuberculosis (Mtb) is necessary for the design of improved therapies. Clustered regularly interspaced short palindromic repeat interference (CRISPRi) has been previously utilized in mycobacteria to identify novel drug targets by the demonstration of gene essentiality. The work presented here shows that it can also be usefully applied to the study of non-essential genes involved in antibiotic resistance. The expression of an ADP-ribosyltransferase (Arr) involved in rifampicin resistance in Mycobacterium smegmatis was silenced using CRISPRi and the impact on rifampicin susceptibility was measured. Gene silencing resulted in a decrease in the minimum inhibitory concentration (MIC) similar to that previously reported in an arr deletion mutant. There is contradictory evidence for the toxicity of Streptococcus pyogenes dCas9 (dCas9_Spy) in the literature. In this study the expression of dCas9_Spy in M. smegmatis showed no impact on viability. Silencing was achieved with concentrations of the aTc inducer lower than previously described and with shorter induction times. Finally, designing small guide RNAs (sgRNAs) that target transcription initiation, or the early stages of elongation had the most impact on rifampicin susceptibility. This study demonstrates that CRISPRi based gene silencing can be as impactful as gene deletion for the study of non-essential genes and further contributes to the knowledge on the design and induction of sgRNAs for CRISPRi. This approach can be applied to other non-essential antimicrobial resistance genes such as drug efflux pumps.

Inactivation of bpsl1039-1040 ATP-binding cassette transporter reduces intracellular survival in macrophages, biofilm formation and virulence in the murine model of Burkholderia pseudomallei infection

Burkholderia pseudomallei, a gram-negative intracellular bacillus, is the causative agent of a tropical infectious disease called melioidosis. Bacterial ATP-binding cassette (ABC) transporters import and export a variety of molecules across bacterial cell membranes. At present, their significance in B. pseudomallei pathogenesis is poorly understood. We report here characterization of the BPSL1039-1040 ABC transporter. B. pseudomallei cultured in M9 medium supplemented with nitrate, demonstrated that BPSL1039-1040 is involved in nitrate transport for B. pseudomallei growth under anaerobic, but not aerobic conditions, suggesting that BPSL1039-1040 is functional under reduced oxygen tension. In addition, a nitrate reduction assay supported the function of BPSL1039-1040 as nitrate importer. A bpsl1039-1040 deficient mutant showed reduced biofilm formation as compared with the wild-type strain (P = 0.027) when cultured in LB medium supplemented with nitrate under anaerobic growth conditions. This reduction was not noticeable under aerobic conditions. This suggests that a gradient in oxygen levels could regulate the function of BPSL1039-1040 in B. pseudomallei nitrate metabolism. Furthermore, the B. pseudomallei bpsl1039-1040 mutant had a pronounced effect on plaque formation (P < 0.001), and was defective in intracellular survival in both non-phagocytic (HeLa) and phagocytic (J774A.1 macrophage) cells, suggesting reduced virulence in the mutant strain. The bpsl1039-1040 mutant was found to be attenuated in a BALB/c mouse intranasal infection model. Complementation of the bpsl1039-1040 deficient mutant with the plasmid-borne bpsl1039 gene could restore the phenotypes observed. We propose that the ability to acquire nitrate for survival under anaerobic conditions may, at least in part, be important for intracellular survival and has a contributory role in the pathogenesis of B. pseudomallei.

Trehalose dimycolate interferes with FcγR-mediated phagosome maturation through Mincle, SHP-1 and FcγRIIB signalling

The causative agent of tuberculosis, Mycobacterium tuberculosis (M. tuberculosis), contains an abundant cell wall glycolipid and a crucial virulence factor, trehalose-6,6’-dimycolate (TDM). TDM causes delay of phagosome maturation and thus promotes survival of mycobacteria inside host macrophages by a not fully understood mechanism. TDM signals through the Monocyte-INducible C-type LEctin (Mincle), a recently identified pattern recognition receptor. Here we show that recruitment of Mincle by TDM coupled to immunoglobulin (Ig)G-opsonised beads during Fcγ receptor (FcγR)-mediated phagocytosis interferes with phagosome maturation. In addition, modulation of phagosome maturation by TDM requires SH2-domain-containing inositol polyphosphate 5’ phosphatase (SHP-1) and the FcγRIIB, which strongly suggests inhibitory downstream signalling of Mincle during phagosome formation. Overall, our study reveals important mechanisms contributing to the virulence of TDM.

Mycobacterium leprae Activates Toll-Like Receptor-4 Signaling and Expression on Macrophages Depending on Previous Bacillus Calmette-Guerin Vaccination

Toll-like receptor (TLR)-1 and TLR2 have been shown to be receptors for Mycobacterium leprae (M. leprae), yet it is unclear whether M. leprae can signal through alternative TLRs. Other mycobacterial species possess ligands for TLR4 and genetic association studies in human populations suggest that people with TLR4 polymorphisms may be protected against leprosy. Using human embryonic kidney (HEK)-293 cells co-transfected with TLR4, we demonstrate that M. leprae activates TLR4. We used human macrophages to show that M. leprae stimulation of cytokine production is diminished if pre-treated with TLR4 neutralizing antibody. TLR4 protein expression was up-regulated on macrophages derived from non-bacillus Calmette-Guerin (BCG) vaccinated healthy volunteers after incubation with M. leprae, whereas it was down-regulated in macrophages derived from BCG-vaccinated donors. Finally, pre-treatment of macrophages derived from BCG-naive donors with BCG reversed the effect of M. leprae on TLR4 expression. This may be a newly described phenomenon by which BCG vaccination stimulates “non-specific” protection to the human immune system.

Mincle-mediated anti-inflammatory IL-10 response counter-regulates IL-12 in vitro

The role of macrophage-inducible C-type lectin (Mincle) in anti-inflammatory responses has not yet been fully characterized. Herein, we show that engagement of Mincle by trehalose-dimycolate or mycobacteria promotes IL-10 production in macrophages, which causes down-regulation of IL-12p40 secretion. Thus, Mincle mediates both pro- as well as anti-inflammatory responses.

Shared characteristics between Mycobacterium tuberculosis and fungi contribute to virulence

Mycobacterium tuberculosis, an etiologic agent of tuberculosis, exacts a heavy toll in terms of human morbidity and mortality. Although an ancient disease, new strains are emerging as human population density increases. The emergent virulent strains appear adept at steering the host immune response from a protective Th1 type response towards a Th2 bias, a feature shared with some pathogenic fungi. Other common characteristics include infection site, metabolic features, the composition and display of cell surface molecules, the range of innate immune receptors engaged during infection, and the ability to form granulomas. Literature from these two distinct fields of research are reviewed to propose that the emergent virulent strains of M. tuberculosis are in the process of convergent evolution with pathogenic fungi, and are increasing the prominence of conserved traits from environmental phylogenetic ancestors that facilitate their evasion of host defenses and dissemination.

Exploring the use of strategic frameworks in dental practice

This paper explores the use of strategic frameworks in NHS and private dental practice. It reviews the policy context of dentistry and suggests the challenges in this context will require dental practices to prioritise understanding and engagement with a strategic approach. A strategic approach will be required in order to enhance and improve performance. Two specific strategic frameworks will be explored in terms of their relevance to NHS and private dental practice.

The entrepreneurial role in primary care dentistry

This paper explores the entrepreneurial role of dentists in primary care dentistry. It reviews the changing context of dentistry, not least the reforms being introduced by the health and social care bill. It suggests that this new context will reinforce the need to consider the business side of dental practice, in particular, the importance of quality, creativity and innovation, alongside the importance of meeting the needs of patients. An entrepreneurial approach will be required in order to sustain dental practice in an increasingly competitive environment.

Identification and gene expression of the bovine C-type lectin Dectin-1

C-type lectin receptors (CTLR) are cell-surface signalling molecules that recognize a range of highly conserved pathogen molecules and instigate the appropriate immune response. Here, we report the cloning, sequencing, mapping and expression pattern of the bovine C-type lectin domain family 7, member A (CLEC7A; synonyms CLCSF12, Dectin-1). We identified two isoforms, similar to the human system, with a long and short neck. Overall, the organization of the two bovine CLEC7A genes is similar to that of humans and mice. The CLEC7A gene maps on Bos taurus chromosome 5 (BTA5). mRNA transcripts for CLEC7A were detected in bone-marrow cells, monocytes, macrophages and dendritic cells and NK cells, but not in CD4(+) T-cells or CD21(+) B-cells. The increased knowledge of the genomic organization of the bovine CTLR genes may promote our understanding of their evolution and help in the identification of bovine genes underlying disease-resistance traits.

Managing the 'seamless service': Primary Care Groups in the new NHS

This paper reports on empirical work examining the consequences for the development of the role of Primary Care Groups of the shift from competition (in the internal market) to relationships based on collaboration and partnership. Previous work (Conway and Willcocks, 1998; Willcocks and Conway, 1999) firstly developed a conceptual framework emphasizing the development of relationships between Primary Care Groups and their key stakeholders (for example, Health Authorities, Local Authorities and Trusts) and, secondly, sought to test this framework empirically through case study analysis of two Primary Care Groups in the north of England. This paper takes the research further and focuses on one of these Primary Care Groups, providing an in-depth analysis of particular issues such as the rationale for the particular configuration of this organization and the chosen working arrangements, the role and function of the Board and individual members, and the problems encountered in the first year of operation.

Responding to diversity: the Primary Care Group in the NHS

The paper attempts to examine the development of Primary Care Groups in the NHS, utilising a conceptual framework taken from relationship marketing. In particular, it looks at a framework representing the complex relationships between the Primary Care Group and a diverse range of internal and external stakeholders and the implications of these relationships. It reports the preliminary findings of an ongoing, in-depth case study of two Primary Care Groups; with data collected from in-depth interviews with a small number of key stakeholders. The results, so far, suggest the importance of developing and maintaining longer-term relationships with a range of partners, both internal and external. It recommends that Primary Care Groups should develop strategies to work closely with these stakeholders, as an essential underpinning to developing continuous improvement in performance, quality and "user" retention.

The use of 'expectation enactment' as a conceptual framework for assessing managerial effectiveness: an NHS hospital trust example

This paper examines managerial effectiveness in the National Health Service, utilizing a conceptual framework devised by Fondas and Stewart (1994) which focuses upon the concept of ‘expectation enactment’. The conceptual framework is applied to a National Health Service trust; more specifically, it is used to examine the managerial effectiveness of clinical managers at this trust.

The data for this paper is derived from a larger qualitative study of three NHS case studies. The data was collected from a series of in-depth interviews with clinical managers and general managers. In one of these case studies, part of the analysis was undertaken utilizing concepts put forward by Fondas and Stewart (1994). These will form the basis of this paper.

The development of clinical management at an NHS Trust hospital. A case study example

The article examines and comments on the development of clinical management at an NHS hospital Trust. It utilises a qualitative case study methodology to collect data from key stakeholders at this Trust. The data suggest some of the reasons why doctors may be receptive or non-receptive to the notion of clinical management. It recommends that attention is focused on the specialty context as a key factor in influencing the development of clinical management. It also suggests there may be other important factors, for example: training, the role of change agents; structure of clinical directorates; and individual factors such as cognition, attitudes and motivation.

Strategic marketing and clinical management in health care: a possible way forward

This article examines and comments on the role of clinical directors in the NHS (UK), with specific reference to the relevance of a strategic marketing emphasis. It utilises qualitative methodologies to collect data from stakeholders--in particular, clinical directors and other managers--from two NHS trust hospitals. It examines the extent to which a marketing approach is applicable to clinical managers working in these two hospitals. It utilises a conceptual framework devised by Kottler and Andreason, to highlight whether a marketing approach is, in fact, utilised by these managers. It suggests that a strategic marketing approach (based upon relationships), remains relevant to clinical management, notwithstanding recent changes in government policy.

The role of expectations in the perception of health care quality: developing a conceptual model

Proposes a conceptual model of quality which incorporates an expectation framework. The model was prompted by a related empirical study examining effectiveness in a health care setting which highlighted the importance of quality measures in a contracting environment. The model attempts to understand the relationships between perceived service quality and patient expectations, experience and satisfaction. Makes recommendations which are considered to be relevant to NHS policy makers.

Managerial effectiveness in the NHS. A possible framework for considering the effectiveness of the clinical director

Examines managerial effectiveness in the NHS, in particular the effectiveness of the clinical director. Based on a qualitative study of an NHS Trust hospital case study, utilizes a social cognitive perspective to analyse the data and draw conclusions. Uses the data to suggest a possible framework for examining the effectiveness of individual directors. The framework may be relevant to other messages, particularly those in professional service organizations. It may also be used as a diagnostic tool to assess these managers. The framework is grounded in the perceptions of the interviewees at the Trust: both clinical directors and managers.

The clinical director in the NHS: utilizing a role-theory perspective

Reviews the role of the clinical director in the NHS, based on data collected in a qualitative research study. Utilizes role theory to invite insight into a relatively new but important managerial role. Suggests that effectiveness in the role may be measured by the extent to which managers are able to meet the expectations of their role set, and also that the overall effectiveness of the clinical direction may be the extent to which he or she is able to influence, adapt, modify or change these role expectations.